ARS | Publication request: CHARACTERIZATION AND MAPPING OF RPIL, A LATE BLIGHT RESISTANCE LOCUS FROM DIPLOID (1EBN) MEXICAN SOLANUM PINNATISECTUM

Submitted to: Molecular and General Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 16, 2001
Publication Date: N/A

Interpretive Summary: Wild Solanum species grow naturally from the southwestern United States to central Chile and show many resistances to economically important disease of the cultivated potato. Research has focused on wild species that easily cross with the cultivated potato. Wild Mexican Solanum species have received less attention because of poor crossability with cultivated potato. Late blight is a devastating fungal disease of potato caused by Phytophthora infestans. We characterized resistance to P. infestans in the Mexican species Solanum pinnatisectum. A hybrid between resistant S. pinnatisectum and susceptible S. cardiophyllum plants was backcrossed to S. cardiophyllum to generate a family segregating for late blight resistance. A genetic map generated with 99 differences in the DNA and revealed a single dominant resistance gene, named Rpi1, on chromosome 7. This chromosome region has not been associated with late blight resistance, indicating that this could be a new resistance gene. These results will be of interest to potato breeders and pathologists who can use this gene as a new source of resistance to late blight.

Technical Abstract: Solanum is a diverse genus with over 200 species ranging from the southwestern United States to central Chile. Germplasm evaluations have focused on species crossible with S. tuberosum, while Mexican diploid (2n=2x=24) Solanum species with an Endosperm Balance Number (EBN) of one have received less attention because of poor crossability due to ploidy and EBN. Recent changes in Phytophthora infestans populations have increased the need for new sources of genetic resistance. We have characterized resistance to P. infestans in the Mexican 2x(1EBN) species S. pinnatisectum. An interspecific hybrid between resistant S. pinnatisectum and susceptible S. cardiophyllum plants was backcrossed to S. cardiophyllum to generate a family segregating for late blight resistance. The diploid (1EBN) genetic map generated with 99 RFLPs revealed extensive synteny with previous published potato maps. A single dominant late blight resistance locus (Rpi1) from S. pinnatisectum was mapped to chromosome 7, a region previously unassociated with late blight resistance.